1. Field of the Invention
The present invention relates to a control device for an in-cylinder fuel injection type internal combustion engine.
2. Background Art
An in-cylinder injection type internal combustion engine which injects fuel directly into a cylinder is widely known. The in-cylinder injection type internal combustion engine performs direct fuel injection into a combustion chamber by means of a fuel injection valve, and is intended to achieve a reduction in exhaust gas substance and fuel consumption, enhancement in output, and the like.
In the in-cylinder injection type internal combustion engine, the injected fuel may attach to a piston crown surface or a cylinder bore wall surface depending on a fuel injection start timing.
If an amount of fuel attaching and remaining on the cylinder bore wall surface is large, such fuel cannot be vaporized completely until ignition in some cases, so that unburned gas is apt to increase. Therefore, for example, JP Patent Publication (Kokai) No. 2009-102997 and JP Patent Publication (Kokai) No. 2009-102998 each disclose a technology of changing, when a temperature on the cylinder bore wall surface is low, the fuel injection start timing from an injector in an intake stroke so that the fuel spreads over the piston crown surface to be easily vaporized.
In addition, JP Patent Publication (Kokai) No. 2002-161790 discloses a technology in which: fuel injection is performed a plurality of times in one cycle, and the fuel injection amount for each time is accordingly made smaller, to thereby reduce the fuel attachment to the cylinder bore wall surface; and an interval between one injection and the next injection is kept constant at a rough crank angle with respect to a change in operation conditions of an engine, that is, the injection interval is set to be longer as the rotation becomes lower and is set to be shorter as the rotation becomes higher, to thereby decentrally spray the fuel.
On the other hand, if an amount of fuel attaching and remaining on the piston crown surface and the cylinder bore wall surface is large, the number of exhaust particles of particulate matters (hereinafter, referred to as PM) is apt to increase. In particular, if the amount of fuel attaching on the piston crown surface is large, the number of exhaust particles of PM is apt to increase. In recent years, there is an increasing need for the in-cylinder injection type internal combustion engine to reduce the number of exhaust particles of PM.